To extinguish a fire in an enclosed space it is known to create in the enclosed space an atmosphere which prevents combustion. Inert solvents (carbon dioxide, nitrogen, argon, water vapour), volatile inhibitors, halogenated agents or extinguishing powders (A. N. Baratov, E. M. Ivanov "Extinguishing fires in the chemical and oil-refining industries", Moscow, Chemistry, 1979) are used as fire extinguishing agents.
The known fire extinguishing systems for fires in enclosed spaces cannot be used, however, for extinguishing alkalimetals and alkaline earth metals and some metal hydrides and metal compounds which contain oxygen in their molecules.
The construction of fire extinguishing systems for rooms in very large buildings is difficult, because an adequate amount of gas has to be made available in a certain time. In addition, because of the danger of suffocation, signalling systems that indicate the implementation of the extinguishing process are necessary.
The use of halogenated compounds to extinguish fire likewise has a number of drawbacks. The effect of these agents on humans can be toxic, since their thermal decomposition when extinguishing fire gives rise to products having a highly corrosive action.
In addition, enclosed spaces at particular risk from fire are normally protected by very large fire-extinguishing systems employing halogenated hydrocarbons. On account of international measures for protection of the ozone layer in accordance with the Montreal protocol (1987), fluorohydrocarbons need to be reduced by half by 1995 and to be eliminated completely by the year 2000, since the potential of these substances to destroy ozone is high.
Fire-extinguishing systems having devices to produce fluorocarbon compounds are already known, for example from GB-PS 2 020 971. The disadvantage of these systems is the damaging effect of the fluorocarbon compounds on the environment. In addition, these systems have fairly large dimensions and are fairly heavy, so that they cannot be used very effectively to extinguish fires in means of transportation, for example, in air traffic.
GB-PS 2 028 127 discloses a fire extinguishing device having a housing with a discharge opening, a charge for producing the fire-extinguishing substance, and an ignition unit. When the ignition unit is operated, the pyrotechnic or solid-fuel charge is ignited, and the gaseous combustion products thereof form the fire extinguishing substance that passes through the discharge opening into the fire region and extinguishes the fire. The effectiveness of this apparatus is unsatisfactory, however, since the capacity of the gaseous combustion products, which are inert solvents, to extinguish fire is slight.
PCT/RU 92/00071 discloses a method for producing a fire-extinguishing mixture in which a mixture of solid particles and inert gases is produced on letting off the charge comprising a pyrotechnic composition. The high dispersion degree of these particles, their chemical property and the freshly formed surface ensure a substantial fire-extinguishing action.
That method has a number of drawbacks, however. The high temperature of the combustion products leads to an increase in the average temperature in the enclosed space to be protected, which has an adverse effect on living things in this enclosed space and on valuables (for example, documents, paintings etc.). As the aerosol cools, the proportion of unreacted elements in the combustion products, and consequently also the proportion of NH3, CO, nitrogen oxide and other products in the fire-extinguishing agent, increases dramatically. In addition, on combustion of the pyrotechnic, solid-fuel, aerosol-forming fire-extinguishing mixture compositions and ballistic compositions, in addition to the primary gaseous aerosol products having the extinguishing action, gaseous products of the incomplete combustion of organic components (NH3, H2, CHx) and nitrogen oxides (NOx) are also released, which leads to pollution of the environment by these products.